Method and device for controlling a hydraulic actuator

Abstract

A method, device, and control unit for controlling an actuator in open loop, particularly for a valve, preferably for a gas-exchange valve of an internal combustion engine, having at least one control valve for opening the valve and one control valve for closing the valve, each of the control valves being capable of being driven by at least one drive pulse whose duration determines a position on the positioning travel of the valve. The valve is opened / closed in one lift and / or a plurality of partial lifts and at least one drive pulse is assigned to each lift and / or each partial lift, and the valve is assigned at least one transducer which generates a signal that discloses values of a discrete positioning travel of the valve and of an assigned time and / or of a discrete instant and of an assigned positioning travel. The method for controlling the actuator includes:a. Starting of a drive pulse having a setpoint duration of the drive pulse for opening and / or closing the valve,b. Generating at least one signal, andc. Correcting the setpoint duration of the drive pulse and / or of a following drive pulse assigned to the lift and / or to a partial lift, in accordance with the signal.

Description

CROSS REFERENCE[0001]This application claims benefit under 35 U.S.C. § 119 of German Patent Application No. 102007025619.3, filed no Jun. 1, 2007, which is expressly incorporated herein by reference in its entirety.FIELD OF THE INVENTION[0002]The present invention relates to a method for controlling an actuator in open loop, particularly for a valve, preferably for a gas-exchange valve of an internal combustion engine, having at least one control valve for opening the valve and one control valve for closing the valve, each of the control valves being capable of being driven by at least one drive pulse whose duration determines a position on the positioning travel of the valve. The present invention further relates to a corresponding device and a corresponding control unit.BACKGROUND INFORMATION[0003]Conventional methods of this kind for controlling an actuator, particularly for hydraulic actuators of the type indicated at the outset, are used for actuating valves such as the gas-exc...

AI Technical Summary

Benefits of technology

[0017]An object of the present invention is to provide a valve-lift control, improved on the basis of a positioning-travel feedback, which ensures the required high actuator precision even in the event of highly dynamic changes of influence variables and large possible errors in determining such influence variables, and in particular, avoids transient errors of the set valve lift.

[0036]A third exemplary embodiment represents the last-named class of design approaches according to the present invention by way of example. The illustratively indicated and very simple iterative correction method is based on the direct evaluation of the positioning travel and velocity for the continual determination of the remaining lift time still necessary, and therefore the driving time in total. This leads—during the already ongoing generation of the drive pulse of a high-pressure-side control valve (MV1) by the appropriate pulse-output unit—to a successive correction of the driving time, that is, of the setpoint value, transmitted to the pulse-output unit, for the pulse length of the already ongoing drive pulse. A prerequisite for this method is a sensor which makes it possible to determine the positioning travel of an EHVC actuator with high accuracy and sampling rate and with not too great a (known) latency. In this context, the necessary sampling rate may be reduced decidedly by a temporal refinement of a roughly sampled input signal, e.g., by the use of a model-based or signal-based extrapolation.

[0044]In one advantageous embodiment of the present invention, the opening of the control valve on the high-pressure side while the control valve on the low-pressure side is in the closed state causes the gas-exchange valve to open, and the opening of the control valve on the low-pressure side while the control valve on the high-pressure side is in the closed state causes the gas-exchange valve to close.

Problems solved by technology

A general disadvantage of these conventional design approaches is that they have to rely on a very good prediction of the possible actuator progressions, and therefore involve a high modeling and / or application expenditure in order to achieve the required actuator precision.

In part, they are rapidly changeable, such as the oil pressure, and / or are difficult to model, like the gas forces, for instance.

In the case of the EHVC system indicated, the basic requirement for a practical application or transfer of the conventional design approaches, i.e., for a regulation of the movement characteristic is not fulfilled, since a proportional driving and therefore producible positioning-force regulation is not possible as a matter of principle.

In addition, errors in determining influence variables are not or are scarcely offset by an adaptation, and are only partially offset by a cycle-based regulation.

Therefore, in spite of available feedback about the adjusted lifts, rapid changes of influence variables such as the oil pressure or of setpoint values of individual valve parameters almost unavoidably lead to noticeable transient setpoint / actual deviations of the valve lift.

Therefore, the feedback about the movement characteristic also contains no information whatsoever about an implemented correction of the driving, since this correction really does not become effective immediately, but only at the end.

Such large errors may occur, for example, in an operating state with high performance demand on the engine in the event of a combustion miss, thus, given the almost complete omission of a normally expected gas force to be kept high at an exhaust valve, if the driving time of the exhaust valve calculated for the normal case is not corrected.

In the design approach presently described, such circumstances are corrected automatically, since the faster opening of the exhaust valve leads to a corresponding (sharp) shortening of the driving time.

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